Abrasive articles



Patented Sept. 24, 1946 I ABnAsIvE Anrrcms Samuel S. Kistler, West Boylston; Mass, assign'oi to Norton Company, Worcester, Mass, a cor- V po'ration of Massachusetts 1 4 7 No Drawing.

' Application .ilanuary 24, (1948,

serial No. 643,202: l J

r: 1: I The finvention relates to abrasive articleseind more particularly to grinding. wheels.

One object of the invention is to provide an active :filler for grinding wheels and other abrasive products, particulamy :ror organic bonded products, which improves the: quality thereof. Another object of the invention is to provide a filler with a higher :quality number Q where.

where is a constant, M is material removed and is wheel wear. Another object of the invention is to provide a filler which gives a higher ratio of material removed to wheel wear. Other objects will be in part obvious or in part pointed out'hereinafter. V I

Efficiency of grinding wheels .has some'times in the past been stated'in terms of ratioo'f material removed to wheel wear. This quite accurately gives the economy of grinding so 'far as the cost of abrasive is concerned, if like quantities of abrasive are assumed to cost likeamounts. But let us assume two wheels having the same ratio in a given grinding job but where the material removed by wheel A in a given time is twice-that removed by wheel B in the same time. Clearly wheel A is commercially preferable for SllChjOb because the labor cost and overhead are half of that {for wheelB. 'No one formulaior determin- 'ing the most economical wheel under all conditions of labor cost and'overhead can be devised. It-happens, however, that the expression M W measures the economy of grinding wheels in many grinding operations providing a large a1- .l'owance 'for labor cost and also for overhead; It can be generalized that in most d-ry snagging "operations the true economy is "an expression.

"where -11. is a number between 1 and 2. -:In the rcrmi-fla I in otherwise identical grinding wheels grinding simply to make the figures in a comparison of fillers .of the above patents, Other 5 Claims. (01-. 51- 367) under the same conditions, one which gives a higher Q number where and which also has a higher ratio where ratiois a superior filler for most dry snagging operaions.

In accordance with my invention 1 have found that the quality and economy of abrasive articles, and particularly grinding wheels, may be mater ially improved by incorporating therein the combination of potassium fluoborate (-KBF4) and iron sulphide such as troilliteiFeS) or pyrites and marcasite (FeSz). Each or these has prelviously been used. In :my Patent No. 2308 981 there is described and claimeda filler of iron sul- L-phide. .Inmy Patent No. 2,308,983 there is described 'and claimed an alkali metal fluoborate specifically potassium fluoborate. Of these, two fillers potassium fiuoborate was found to be superior for most snagging operations. I; have now made, the surprising discovery that the use of :both. of these fillers in combinationqgives better grinding results as measured both: by quality number Q and by ratio of material removed to wheel wear than the use of'either of them alone. This indicates that there may besome interaction between the two compounds and iron or steel beingground which. is different from the action of either of them on the iron or steelbeingground or the sum of such actions. Otherwise it would seem to be clear that the mixture of the two fillers would produce a result which is the mean of the results produced by thesefillers alone. l

The filler of the invention has been used in grindingwheels for snagging operations consisting of fused alumina abrasive bondedjwith phenol formaldehyde ibond. The manufacture of such grinding wheels is inow we'll knownand for the general procedure reference may be had to either abrasives may be used such as silicon carbide and other bonds such as rubber or synthetic rubber and the com- Jaination filler of this invention may be :intro- "duced'into the pores of a vitrified ceramic bon-ded grinding wheel.

' Five wheels were made from No. 12 grit size A1203 bonded with phenol formaldehyde, all

wheels being 16" in diameter by 2" thick with a 6" diameter central hole. In accordance with The Wheels were then tested under identical conv ditions with a swing frame grinder grinding 18-8 Allegheny steel with 140 pounds of total pressure between wheel and work at a speed of 9500 surface feet per minute.

Table 1 gives the wheel number, the filler and percentage thereof by volume of the total bond and filler, the wheel wear in cubic inches per hour W, the material removed in pounds per 1 hour M; the quality number as represented by the expression M2 w I the ratio of material removed .to wheel wear and a designation of the day on which the grinding was done.

Table 1 Wheel M M number Filler W M KW W Day 10.7 9.3 14 0.869 No.1 12. 8 10.0 16 .828 No. 2 13. 5 11.3 17 837 N0. 2 10. 8 9. 1 14 .843 No. 1 13. 0 12.0 923 No. 2

Seven wheels were made to a size 16" in diameter by 2.5" thick with a 6" diameter central hole out of No. 12 grit size A1203 which was first wet with furfural after which reactive phenol formaldehyde resin containing5% CaO by volume on the total bond and filler was added. These wheels were tested under identical conditions in a swing frame grinder grinding bullet steel with a total pressure of 175 pounds between the wheel and the work and at a speed of 9500 surface feet per minute. The :wheels had different fillers as indicated in Table 2, the headings whereof have the same meaning as in Table --1. All these wheels had the same structure namely 54 volume per cent of abrasive, 34 volume per cent of bond including filler. and the lime, leaving 12% pores.

Table 2 1 Wheel l v t M M .number Filler W M KT W VDvay XL276 cryolite 30.0 18.3 20' 0010 No.3 XL1l39-l do 24.7 17.9 23 .725 No.4 XL1l392 .do 24.2 17.4 22 .719 No.4 XL278 12.5% cryolite+ 30.0 19.3 22 .643 No.8

' 12.5% KBF4. XLll341 12.5% cryolite+ 20.2 18.2 23 .095 No.4

12.5% Keri. XL277 12 %esi+12.5% 29.2; 2. .757 o.8

' .4- 5 l XL11340 12.5% FeSz%l2.5% 23.0 20.2 -32 .878 No.4

Evaluating the figures in Table land Table;2 -it is seen that whether valuated by quality numher or by ratio of material removed to wheel wear, Fesz for grinding stainless steel is no better than cryolite. It also appears that for grinding stainless steel potassium fluoborate is superior to either cryolite or FeSz. On the other hand the combination of cryolite and potassium fiuo- .borate is ,no better than cryolite for grinding bullet steel. 'And the combination of FeS2 and potassium fluoborate is definitely superior to cryolite for the grinding of bullet steel. Furthermore, as measured by the quality number the margin of superiority of Fesz plus KBF4 over the standard filler cryolite is greater than the margin of superiority of KBF4 over cryolite.

For the manufacture of grinding wheels bonded with other bonds one may proceed as explained in my Patents No. 2,308,981 and 2,308,983 which describes the manufacture of grinding wheels bonded with aniline formaldehyde, with rubber, and the manufacture of vitrified grind.- ing wheels. i

In the case of any organic bonded wheelthe filler of this invention, KBF4+iron sulphide, is incorporated in the bond. In the case of a vitrified grinding Wheel, the wheel is first made in the usual manner and then the pores thereof are impregnated with the filler suspended in a supplemental bond, all as fully explained in each of Patents No. 2,308,981 and 2,308,983.

It will thus be seen that there has been provided by this invention grinding wheels and other abrasive articles in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set'forth is to be interpreted as illustrative and not in alimiting sense.

I claim: 5

1 An abrasive article comprising abrasive grains, a bond uniting the grains as an integral body, and the combination of iron sulphide and potassium fiuoborate interspersed throughout the bonded mass. g r

2. An abrasive article comprising abrasive grains, an organicbond unitingthe grains as an integral body, and filler of finely divided solid iron sulphide and potassium fiuoborate interspersed throughout the bond. I

3. An abrasive article comprising abrasive grains and a resinoid bond which unites the grains as an integral body, said bond having intimately associated therewith filler comprising iron sulphide and potassium fiuoborate.

4. An abrasive article comprising abrasive grains and a phenol formaldehyde bond which unites the grains asan integral body, Such bond having. intimately associated therewith filler comprising iron sulphide and potassium fluoborate.

5. An abrasive article comprising abrasive grains, an organic bond uniting the grains as an integral body, and a filler comprising a :combination of Fesz and K BF4.

SAMUEL S. KISTLER. 

